Diet fatty acid profile, membrane composition and lifespan: an experimental study using the blowfly (Calliphora stygia).

The membrane pacemaker theory of ageing proposes that the polyunsaturated fatty acid (PUFA) composition of membrane lipids of a species is an important determinant of its maximum lifespan. We report three experiments using the blowfly Calliphora stygia, where this theory was tested by manipulation of dietary fat profile. Although the fat profile of the larval diet resulted in small alterations of individual membrane fatty acids, it had no effect on the peroxidation index (PI) of membrane lipids and furthermore had no effect on maximum lifespan. Similarly, manipulation of the fat profile of the adult diet resulted in small changes in individual fatty acids, but had no effect on the PI of membrane lipids. There was a small increase in maximum lifespan when adult diet was supplemented with PUFA in form of vegetable oils but no effect when diet was supplemented with pure PUFA. This difference is possibly due to antioxidant content of vegetable oils. The relative refractoriness of membrane PI to dramatic changes in response to diet is similar to the situation in the rat. These results also indicate the blowfly is unable to convert 18-carbon PUFA to more highly polyunsaturated 20- and 22-carbon PUFA.

Dietary n-3 and n-6 fatty acids alter avian metabolism: metabolism and abdominal fat deposition.

The effects of dietary saturated fatty acids and polyunsaturated fatty acids (PUFA) of the n-3 and n-6 series on weight gain, body composition and substrate oxidation were investigated in broiler chickens. At 3 weeks of age three groups of chickens (n 30; ten birds per group) were fed the fat-enriched experimental diets for 5 weeks. These diets were isonitrogenous, isoenergetic and contained 208 g protein/kg and 80 g edible tallow, fish oil or sunflower oil/kg; the dietary fatty acid profiles were thus dominated by saturated fatty acids, n-3 PUFA or n-6 PUFA respectively. Resting RQ was measured in five birds from each treatment group during weeks 4 and 5 of the experiment. There were no significant differences between treatments in total feed intake or final body mass. Birds fed the PUFA diets had lower RQ and significantly reduced abdominal fat pad weights (P<0.01) compared with those fed tallow. The dietary lipid profile changes resulted in significantly greater partitioning of energy into lean tissue than into fat tissue (calculated as breast lean tissue weight:abdominal fat mass) in the PUFA groups compared with the saturated fat group (P<0.01; with no difference between the n-3 and n-6 PUFA groups). In addition, the PUFA-rich diets lowered plasma concentrations of serum triacylglycerols and cholesterol. The findings indicate that dietary fatty acid profile influences nutrient partitioning in broiler chickens.